In recent years, storage virtualization technology in a computer system is being broadly proposed. For example, PTL 1 discloses technology which enables a first physical storage apparatus to virtualize a logical volume of a second physical storage apparatus and provide such virtualized logical volume to a host computer as a logical volume in the own physical storage apparatus. Based on this storage virtualization technology, the storage capacity of the first physical storage apparatus can be extended by connecting the first physical storage apparatus to the second physical storage apparatus.
Meanwhile, PTL 2 discloses technology of consolidating the logical pools created in a first physical storage apparatus and a second physical storage apparatus based on the thin provisioning technique. The thin provisioning technique is the technique of a host computer dynamically assigning a storage area storing data from a logical pool according to a write request from the host computer. Based on the consolidation of the logical pools as described above, a virtual logical volume (this is hereinafter referred to as the “virtual volume”) created in the second physical storage apparatus can be used as the virtual volume in the first physical storage apparatus.
Moreover, by using the technology disclosed in PTL 2, it is also possible to assign a storage area from a plurality of physical storage apparatuses to one virtual volume. In PTL 2, each physical storage apparatus manages configuration information which associates all logical pools, the respective virtual volumes associated with the respective logical pools, and unit-based physical storage areas (these are hereinafter referred to as the “physical pages”) respectively configuring the respective logical pools. If the configuration information related to the logical pages is used as an identifier of the physical storage apparatus in which the respective logical pages are disposed and an address of the physical area that is being used in that physical storage apparatus, even if there are a plurality of physical storages apparatus to assign a storage area to one virtual volume, it is possible to manage the configuration information of the respective virtual volumes.
In addition, PTL 3 discloses technology of determining whether an I/O (Input/Output) request given from a host computer is directed to an own physical storage apparatus, and, when the I/O request is directed to another physical storage apparatus connected to the own physical storage apparatus, transferring that I/O request to the other physical storage apparatus.